Yesterday CommanderBond.Net were the first site to post this publicity image from Die Another Day;

An investigation was recently started in the thread of the Die Another Day Forums that is discussing the new images, and it's been revealed that this station that Bond and Q can be seen in is part of the Piccadilly Line. James Page suggests from the viewable sign that this particular station is Down Street.

This theory does make sense. Down Street is a part of the Piccadilly Line. Also the Piccadilly Line has been closed down since before the Second World War (hence the nostalgic posters in the background). Down Street itself was closed off in 1932 and during the Second World War was converted into offices for the Railway Executive Committee and for the War Cabinet. It is believed that Winston Churchill had an office in this section of the Underground.

Above is an image of the entrance to the Underground on Down Street as it stands today. Tourists are allowed to visit the close off section, however, there is currently a waiting list of 3,000 people.

With it's history Down Street seems the perfect place for MI6 to have a secret base.